A downhole perforating gun can be an example of a downhole tool and can include an explosive that can be discharged to generate one or more openings in a downhole structure and, for example, a surrounding geologic environment. As an example, such one or more openings may be utilized for fluid flow. For example, liquid and/or gas in a reservoir may flow via such one or more openings. As an example, fluid may be injected into a geologic environment via such one or more openings.